Exhibit 10.21

TRANSITION SERVICES AGREEMENT

This TRANSITION SERVICES AGREEMENT (this “ Agreement ”), dated as of April 1, 2004, is entered into by and among ICG Telecom Group, Inc., a Colorado corporation (“ ICG ”) and Level 3 Communications, LLC, a Delaware limited liability company (“ Level 3 ”).

WHEREAS , ICG (and its parent company) and Level 3 have entered into an Asset Purchase Agreement, dated as of April 1, 2004 (the “ Purchase Agreement ”), relating to the purchase and sale of the certain assets and the assumption of certain liabilities relating to the Business;

WHEREAS , pursuant to the Purchase Agreement certain Numbers used in the Business will not be transferred or assigned to Level 3 until after Closing;

WHEREAS , after the Closing and in order to provide service under the Customer Contracts which have been conveyed and assigned to Level 3, Level 3 will require for a limited period of time the use of services to be delivered by ICG to Level 3 using certain Numbers that have not yet been transferred or assigned to Level 3;

NOW, THEREFORE , in consideration of the mutual covenants and agreements contained herein and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree as follows:

ARTICLE I.

DEFINITIONS

Capitalized terms used but not otherwise defined herein shall have the meanings specified in the Purchase Agreement.  In addition, the following capitalized terms shall have the meanings set forth below:

“ A Numbers ” shall mean those Numbers delineated as such on tabs 5, 6 and 7 of the spreadsheet attached as Exhibit B .

“ B Numbers ” shall mean those Numbers delineated on tabs 5, 6, and 7 of the spreadsheet attached as Exhibit B .

 “ ICG Underlying Service Contracts ” are those agreements, understandings or contracts necessary to provide the ICG Transition Services, including, without limitation, those agreements delineated on Exhibit A hereto.

“ Number Termination Notice ” shall mean a notice delivered by Level 3 to ICG, whereby Level 3 notifies ICG that Level 3 no longer needs ICG Transition Services with respect to those Numbers delineated in such notice.

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“ POP ” is a point of presence used by ICG in the operation of the Business, as delineated on tabs 2 and 3 of the spreadsheet attached as Exhibit B .

 “ Retained Numbers ” shall mean those Numbers, the use of which, as of the Closing, has not yet been transferred or assigned to Level 3, and which are temporarily retained by ICG pursuant to the terms of the Purchase Agreement and this Agreement.

“ Retained POP ” shall mean a POP, the use of which has not yet been terminated pursuant to Section2.1 hereof.

“ Retained Uncovered LATA ” shall mean an Uncovered LATA, the services within which have not yet been terminated pursuant to Section 2.1 hereof.

“ Services ” shall mean, collectively, ICG Transition Services and Migration Services, as hereinafter defined.

“ Uncovered LATA ” is an uncovered Local Access and Transport Area in which ICG operates the Business, as delineated on tab 4 of the spreadsheet attached as Exhibit_B .

ARTICLE II.

PROVISION OF SERVICES BY ICG

Section 2.1.           ICG Transition Services .  ICG shall provide to Level 3, with respect to any Assumed Customer Contract, access to and use of the Retained Numbers and any goods and services provided to ICG related thereto (or which ICG has the right to obtain under the terms of its existing contractual arrangements) in connection with the Business, including, without limitation, those services described on Exhibit C (collectively, the “ ICG Transition Services ”) as of the date of the Purchase Agreement during the period (the “ ICG Service Period ”) from the Closing Date until, with respect to each Retained Number, each Retained POP, and each Retained Uncovered LATA, the first to occur of the following (each an “ Effective Date ”):

(a)           with respect to a Retained Number, 15 days after delivery of a Number Termination Notice delineating such Retained Number; provided, however, the ICG Service Period for any Retained Number used by ICG in providing services to a customer under an Excluded Customer Contract shall be deemed to end (and the Effective Date shall be deemed to have occurred) as of the Closing Date, without further notice from Level 3; and

(b)           with respect to a POP, 30 days after the delivery of a Number Termination Notice for the last Retained Number corresponding to such POP; provided, however, that the ICG Service Period for any POP used by ICG solely in providing services to any customer(s) under any Excluded Customer Contract(s) shall be deemed to end (and the Effective Date shall be deemed to have occurred) as of the Closing Date, without further notice from Level 3.

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(c)           with respect to an Uncovered LATA, 30 days after the delivery of a Number Termination Notice for the last Retained Number corresponding to such Uncovered LATA; provided, however, that the ICG Service Period for any Uncovered LATA used by ICG solely in providing services to any customer(s) under any Excluded Customer Contract(s) shall be deemed to end (and the Effective Date shall be deemed to have occurred) as of the Closing Date, without further notice from Level 3.

(d)           the effective date of termination of the ICG Service Period, as set forth in written notice from Level 3 to ICG.

Each of Level 3 and ICG acknowledge and agree that upon receipt by ICG of any Number Termination Notice, ICG will have the right to terminate (subject to the terms of this Section 2.1 and Exhibit D hereto) the Services with respect to the applicable Number (as set forth in such Number Termination Notice), POP (if such Number Termination Notice requests termination of the last Retained Number corresponding to such POP), or Uncovered LATA (if such Number Termination Notice requests termination of the last Retained Number corresponding to such Uncovered LATA).

Section 2.2.           Pass Through Rights .  The ICG Transition Services shall be provided by ICG to Level 3 in substantially the same manner and on substantially the same basis (including as to policies, procedures, practices and timeliness) as the goods and services provided to ICG under existing contractual arrangements relating to the Business.  Without limiting the generality of the foregoing, ICG agrees to perform the ICG Services to the standards and service levels set forth in the respective Assumed Customer Contracts (“ SLA Standards ”).  If and to the extent that ICG is or becomes entitled to exercise any rights or remedies from underlying carriers or subcontractors used to deliver the ICG Transition Services, and if and to the extent ICG does not promptly enforce such rights and remedies, ICG hereby assigns such right and remedies to Level 3 with respect to the ICG Transition Services.  ICG agrees to enforce and prosecute such rights and remedies upon consultation with Level 3 with respect thereto.

Section 2.3.           SLA Remedies .  In the event ICG fails to perform the ICG Transition Services to the SLA Standards, ICG shall reimburse Level 3 in cash in an amount equal to any payments made or service credits granted by Level 3 to customers under Assumed Customer Contracts relating to such failure to perform the ICG Services to the SLA Standards.  Without limiting the foregoing remedy, Level 3 may, at its option, perform any ICG Transition Services which ICG fails to perform and ICG shall cooperate, and shall cause its employees and agents to cooperate, with Level 3 in such performance of the ICG Transition Services.

Section 2.4.           Actions with Respect to Certain Agreements .  Except as otherwise consented to in writing by Level 3, which consent may be withheld or granted in Level 3’s sole discretion, during the ICG Service Period:

(a)           With respect to each ICG Underlying Service Contract that will or may expire during the ICG Service Period, ICG shall take such steps as are necessary to continue such ICG Underlying Service Contract or otherwise replace the services provided thereunder until the expiration of the ICG Service Period for the respective Number, POP, or Uncovered LATA, as applicable.

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(b)           ICG shall (i) perform in all material respects its obligations under each ICG Underlying Service Contract, and (ii) not settle, release or forgive any claim or litigation or waive any right under any ICG Underlying Service Contract.

(c)